Mycotoxins and other fungal metabolites are thought to serve as chemical defense systems for the fungi that produce them, and may also be of use in protecting the food source from consumption by other organisms [see: D. T. Wicklow, "Ecological Approaches to the Study of Mycotoxigenic Fungi" In Toxigenic Fungi-Their Toxins and Health Hazards, H. Korata et al. (ed.), Elsevier, New York, pp. 78-86, (1984)].
The fungal tremorgenic mycotoxins, a group of metabolites capable of eliciting tremors in vertebrate animals, are produced by fungi that infect field crops such as corn, oats, and barley [K. M. Domsch et al., Compendium of Soil Fungi, Vol. I, Academic Press, New York (1979)]. These crops may also be infested by the corn earworm, Heliothis zea and the fall armyworm, Spodoptera frugiperda [see: C. L. Metcalf et al., Destructive and Useful Insects, McGraw-Hill, New York (1962)].
Approximately 50 fungal tremorgenic mycotoxins have been described and may be divided into several subgroups based on chemical similarity; including the penitrem group, the fumitremorgin-verruculogen group, the paspalitrem group, the tryploquivaline group, and the tetramic acid group. All of these tremorgens have the indole moiety of tryptophan in common. Tremorgenic mycotoxins are produced by such fungi as the genera Penicillium, Aspergillus, and Claviceps [see: R. J. Cole and R. H. Cox, "Tremorgen Group," Handbook of Toxic Fungal Metabolites, Academic Press, New York, p. 355 (1981)].
Other classes of fungal mycotoxins such as aflatoxins and trichothecenes have been reported to be toxic to insects as have certain cyclic peptides produced by microorganisms including the piericidins and destruxins [see: V. F. Wright et al., "Mycotoxins and Other Fungal Metabolites as Insecticides," In Microbial and Viral Pesticides, E. Kurstak (ed.), Marcel Dekker, New York, pp. 559-583 (1982); S. Tamura et al., "Destruxins and Piericidins," In Naturally Occurring Insecticides, M. Jacobsen et al. (eds.), Marcel Dekker, New York, pp. 499-539 (1971); T. Robinson, "The Evolutionary Ecology of Alkaloids," In Herbivores: Their Interaction With Secondary Plant Metabolites, G. A. Rosenthal et al. (eds)., Academic Press, New York, pp. 413-448 (1979)]. Lolitrem neurotoxins which occur in ryegrass have the indole moiety in their chemical structure. The biosynthetic origin of these materials is not known. Lolitrem B has been shown to be toxic to the Argentine stem weevil [Prestidge et al., Chem. Abst. 103:279 (1985)]. However, the fungal tremorgens are a group of mycotoxins that has not been previously evaluated for toxicity to insects.